mineral
Amethyst (Water-Worn Pebble)
Silicon Dioxide (SiO2 with iron impurities)
Hardness: 7 on Mohs scale. Color: Light purple to lavender. Luster: Vitreous to frosty/dull on weathered surface. Crystal Structure: Trigonal. Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.
- Hardness
- 7 on Mohs scale
- Color
- Light purple to lavender
- Luster
- Vitreous to frosty/dull on weathered surface
Identified More mineral →
Explore Amethyst (Water-Worn Pebble) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 on Mohs scale. Color: Light purple to lavender. Luster: Vitreous to frosty/dull on weathered surface. Crystal Structure: Trigonal. Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.
Formation & geological history
Formed in hydrothermal veins and alluvial deposits where quartz crystals containing trace amounts of iron (Fe3+) were exposed to natural irradiation. The rounded, frosted exterior indicates natural stream, river, or ocean wave erosion over extended periods.
Uses & applications
Popular for lapidary work, wire-wrapping, tumbling, gemstone faceting, healing crystal collections, and decorative displays.
Geological facts
Amethyst gets its purple hue from natural gamma radiation acting on trace amounts of iron within the quartz crystal lattice. Stream-rounded 'sea glass' or water-worn amethyst pebbles often have a frosted 'C-shaped' pitted surface pattern due to micro-impacts with other pebbles.
Field identification & locations
Identify by its hardness (scratches glass/steel, cannot be scratched by a knife), rounded water-worn shape with frosted surface micro-fractures, and characteristic translucent purple hue. Commonly found in alluvial gravel deposits in Brazil, Uruguay, Madagascar, and Namibia.
More like this
Other mineral specimens
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Schist
Schist
Metamorphic
Sandstone with Mineral Veining or Crust
Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)
sedimentary
Potassium Feldspar (Orthoclase)
Orthoclase (KAlSi3O8)
mineral
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Nephrite Jade
Nephrite
Mineral/Rock